The invention relates to a fluidic controller which may be of the pneumatic type and which is especially suitable for permitting a change of throttling range without affecting the calibration point of the controller.
The controller includes an outer tube having one end connectable to a source of pressure and the other end connectable to a reference source of pressure, which may be atmosphere, and an inner tube having an output port at one end and an orifice. The inside diameter of the outer tube and the outside diameter of the inner tube are dimensioned to form a restrictive passage between the two ends of the outer tube and the orifice is positionable along this passage. When the first end of the outer tube is connected to an input pressure and the other end of the outer tube is connected to the reference pressure, a linear pressure gradient is developed along the restrictive passage. The orifice of the inner tube may then be positioned to pickoff any pressure along the pressure gradient and to connect that pressure to the output port of the inner tube.
Sliding tube arrangements having an inner tube and an outer tube are known in the prior art. The prior art, however, has failed to appreciate that the sliding tube arrangement may be used in a controller and has failed to recognize the advantages of such a controller.